How to use API to find CIs based on a view?

Basically, I need to find some CIs, which is availabe in an exisiting view. From the Javadoc, I found this:

findConfigurationItem(com.hp.ov.obs.OID view) Find a set of ConfigurationItem objects, using the criteria of a view.

However, I use this: OID viewOid=null; viewOid = OID.parse("00000000-0000-0000-027d-941caca74216"); ciHome1.findConfigurationItem(viewOid);

I got error: java.lang.NullPointerException at com.hp.ov.obs.impl.wf.AppEntityHome.filterViewableTypes(AppEntityHome.java:800) at com.hp.ov.obs.impl.wf.AppEntityHome.find(AppEntityHome.java:754) at com.hp.ov.obs.impl.wf.AppEntityHome.find(AppEntityHome.java:690)